In many realms of technology, fiber composite materials are now being used to improve component properties and especially in order to reduce their weight. The fiber composite material here has at least two main components, namely, a matrix and fibers that are embedded in this matrix and that serve as reinforcement. Only fiber composite materials with a polymer matrix are of interest for the purposes of the present invention. The combination of such fiber composite materials with other materials, especially metals, is a starting point for the development of new lightweight construction technologies, especially in automotive engineering. Here, the special problem arises of ensuring adequate joining of the fiber composite material to the metal. Consequently, there is a need to develop special joining methods when it comes to the production of a plastic-metal hybrid component consisting of a metal body and a fiber composite intermediate that is joined to the body and that is made of a fiber composite material with a polymer matrix.
Commonly used joining methods comprise, for example, the mechanical joining of the fiber composite intermediate to the metal components by riveting, collar joining or tack joining. Moreover, the connection between the fiber composite intermediate and the metal component can also be made by means of an adhesive method. However, classic adhesive methods have the drawback that an adhesive has to be applied and hardened in additional work steps, which makes automation more difficult. Furthermore, the material properties of the adhesive have to be such that an adequately strong adhesive force is established vis-à-vis the fiber composite material on the one hand, and to the metal component on the other hand. Moreover, the other mechanical properties of the adhesive should also be selected in such a way that the advantages of the composite can indeed come to the fore. In the meantime, special melt adhesives have been developed that allow metals to be joined to polymers. For example, European patent specification EP 2 435 246 B1 describes such a melt adhesive on the basis of copolyamide, which permits an integrally bonded connection to the metal surface via isocyanate and epoxide functionalities.
German patent application DE 10 2008 039 869 A1 describes by way of example a method for the production of lightweight components with which an integrally bonded connection of the fiber composite intermediate to the metal body is achieved by applying an adhesive. After the two elements have been combined in a pressing tool, thermal curing is carried out. Additional examples for the use of plastic-metal hybrid components in automotive engineering can be found in German patent applications DE 10 2006 027 546 A1 and DE 10 2006 058 601 A1. Here, too, an integrally bonded connection is created between metal components and the fiber composite intermediate that serves as reinforcement, and this is done by applying a suitable adhesive.
Accordingly, the prior-art integrally bonded joining methods that make use of adhesives exhibit the above-mentioned drawbacks in the method sequence, and these stand in the way of greater automation. In particular, no suitable adhesion promoters are known for the process-integrated joining by means of a pressing method in which polymer materials are joined to metals.